Datasheet

MAX16955
36V, 1MHz Step-Down Controller
with Low Operating Current
9
Maxim Integrated
Pin Configuration
MAX16955
16
TSSOP
+
BST1SUP
15 DH2EN
14 LX3FOSC
13 BIAS4FSYNC
12 DL5SGND
11 PGND6COMP
10 PGOOD7FB
9
TOP VIEW
OUT8CS
EP
Pin Description
PIN NAME FUNCTION
1 SUP
Input Supply Voltage. SUP is the input voltage to the internal linear regulator. Bypass SUP to PGND with
a 1μF minimum value ceramic capacitor. Connect BIAS and SUP to a 5V rail, if available.
2 EN
Active-High Enable Input. EN is compatible with 5V and 3.3V logic levels. Drive EN logic-high to enable
the output or drive EN logic-low to put the controller in low-power shutdown mode. Connect EN to SUP
for always-on operation. Do not leave EN unconnected.
3 FOSC
Oscillator-Timing Resistor Input. Connect a resistor from FOSC to SGND to set the oscillator frequency
from 220kHz to 1MHz. See the Setting the Switching Frequency section.
4 FSYNC
Synchronization and Mode Selection Input. Connect FSYNC to BIAS to select fixed-frequency PWM
mode and disable skip mode. Connect FSYNC to SGND to select skip mode. Connect FSYNC to an
external clock for synchronization. FSYNC is internally pulled down to ground with a 1M resistor.
5 SGND
Signal Ground. Connect SGND directly to the local ground plane. Connect SGND to PGND at a single
point, typically near the output capacitor return terminal.
6 COMP
Error Amplifier Output. Connect COMP to the compensation feedback network. See the Compensation
Design section.
7 FB
Feedback Regulation Point. Connect FB to BIAS for a fixed 5V output voltage. In adjustable mode,
connect to the center tap of a resistive divider from the output (V
OUT
) to SGND to set the output voltage.
The FB voltage regulates to 1V (typ).
8 CS
Positive Current-Sense Input. Connect CS to the positive terminal of the current-sense element. Figure
4 shows two different current-sensing options: 1) accurate sense with a sense resistor or 2) lossless
inductor DCR sensing.